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Herein, three-dimensional reduced graphene oxide/helical carbon nanotubes (RGO/HCNTs) nanocomposites were synthesized by a combined solution-based method and chemical vapor deposition. This synergistic structure of graphene and helical carbon nanotube exhibited large flexibility, rapid transport kinetics, and excellent electrochemical characteristic. The hemoglobin (Hb) was immobilized on the surface of the RGO/HCNTs nanocomposites for amperometric sensing of HO. The dependence of the electrochemical performance of Hb on the composition of RGO/HCNTs composites is systematically investigated by varying the weight ratio of reduced RGO/HCNTs. Compared with alone graphene or HCNTs electrodes modified with Hb, the catalytic current for HO reduction at the Hb-modified RGO/HCNTs electrode increased due to the increase in the surface coverage of Hb and the excellent electrocatalytic activity of RGO/HCNTs. The constructed biosensor displayed a fast electron transfer of Hb and an excellent electrochemical activity for the detection of HO with high selectivity and sensitivity. [ABSTRACT FROM AUTHOR]

A combined chemical vapor deposition with high-pressure annealing has been developed for the production of phosphorus-doped helical carbon nanofibers (P-HCNFs). The resulting P-HCNFs have a large specific surface area, well-defined three-dimensional hierarchical helical structure and rapid apparent heterogeneous electron transfer. Based on the high electrocatalytic activity, the P-HCNFs were used to develop an amperometric sensor for carbendazim detection. The experimental results demonstrated that the sensor is promising for the determination of carbendazim in food samples due to the high sensitivity, wide linear range and low detection limit. [ABSTRACT FROM AUTHOR]

In this study, a novel Pd/Mn 3 O 4 /plait-like carbon nanocoils (Pd/Mn 3 O 4 /CNCs) catalyst is synthesized by a combined chemical vapor deposition and chemical reduction method. The pretreated Mn 3 O 4 nanoparticles are applied as support materials between Pd nanoparticles and CNCs template. The functional CNCs are covered by Mn 3 O 4 nanomaterials, and the metallic Pd nanoparticles are homogeneously deposited onto the Mn 3 O 4 with smaller sizes compared with those of Pd/CNCs and Pd/VX-72. The as-fabricated electrode of Pd/Mn 3 O 4 /CNCs exhibits higher catalytic activity toward the electro-oxidation of ethanol in alkaline media, more excellent poisoning tolerance, and higher stability than other electrodes. This improved performance of the as-prepared electrocatalyst originates from not only the synergetic effects between the Pd nanoparticles and Mn 3 O 4 , but also the intrinsic characteristic of CNCs. [ABSTRACT FROM AUTHOR]

Abstract: Helical carbon nanotubes (HCNTs) as a novel carbon material have been prepared and the catalytic activities of HCNTs-modified glassy carbon electrode (GCE) towards the electrooxidation of uric acid (UA), ascorbic acid (AA), and dopamine (DA) have been investigated. Comparing with the bare GCE, the HCNTs modified GCE (HCNTs/GCE) has higher catalytic activities towards the oxidation of AA, DA, and UA. Moreover, the peak separations between AA and DA, and DA and UA at the HCNTs/GCE are 102 and 245mV, respectively. Thus the simultaneous determination of AA, DA, and UA was carried out successfully. In the co-existence system of AA, DA, and UA, the linear response range for AA, DA, and UA are 7.5–180μM, 2.5–105μM and 6.7–65μM, respectively and the detection limits (S/N =3) are 0.92μM, 0.8μM and 1.5μM, respectively. [Copyright &y& Elsevier]

Abstract: Poly(diallyldimethylammonium chloride) functionalized helical carbon nanotubes (PDDA-HCNTs) were successfully synthesized. The resulting PDDA-HCNTs composite has good conductivity, solubility and ferromagnetic property. The fabricated HCNTs could be conveniently separated and magnetically attached to the magnetic electrode owing to their excellent magnetic properties. An amperometric biosensor was firstly developed based on glucose oxidase (GOD) functionalized PDDA-HCNTs loaded on magnetic glass carbon electrode. The constructed biosensor exhibited excellent electrocatalytic activity and stability for the detection of glucose with a linear range from 5 to 85μM and a low detection limit of 0.72μM at 3σ. The present work offers a new avenue to broaden the applications of HCNTs in electrochemical biosensors. [Copyright &y& Elsevier]

Abstract: The gold nanoparticles/colloidal carbon sphere hybrid material was used for the immobilization of protein, and was developed in biosensing. The hybrid material was fabricated by the assembly of gold nanoparticles onto the surface of colloidal carbon spheres, which constructed a 3D antibody immobilization matrix on the glass carbon electrode and made the immobilized biomolecules hold high stability and bioactivity. After the sandwich-type immunoreaction, the formed HRP-labeled immunoconjugate showed good enzymatic activity for the oxidation of o-phenylenediamine by H2O2. The approach provided a linear response range between 5 and 250ng/mL with a detection limit of 1.8ng/mL. The immunosensor showed good precision, acceptable stability and reproducibility and could be used for the detection of human IgG in real samples, which provided a potential alternative tool for the detection of protein in clinical laboratory. [ABSTRACT FROM AUTHOR]

Abstract: A simple strategy for sensitive detection of human IgG using cadmium ions-functionalized polymer nanospheres as the label is presented. The polymer nanosphere consisted of hard poly-styrene core and biocompatible poly (acrylic acid) (PAA) shell. The carboxyl groups of hydrophilic shell were used to chelated with the cadmium ions, and then conjugate with antibody (Ab2) to fabricate metal ions marked bioconjugates as the label in immunoassay. For constructing the matrix of the immunosensor, the PAA-functionalized carbon nanotubes were used to modify disposable screen printed electrodes for the immobilization of antibody (Ab1). After sandwich immunoreaction, differential pulse voltammetry was used to oxidize the conjuncted cadmium for the detection of antigen. The obtained results provided a linear response range from 0.1 to 35.0pg/mL human IgG with a lower detection limit of 0.06pg/mL, which is prominently improved in comparison with conventional immunoassay. The usage of the chelation reaction offers a simple and convenient route for the preparation of metallo-immunoassay labels, and also avoids the complicated and time-consuming dissolving of metal component for ultrasensitive determination. This approach is expected to have wide applications in protein diagnostics and bioanalysis in the future. [Copyright &y& Elsevier]

Abstract: This paper describes the combination of electrochemical immunosensor using gold nanoparticles (GNPs)/carbon nanotubes (CNTs) hybrids platform with horseradish peroxidase (HRP)-functionalized gold nanoparticle label for the sensitive detection of human IgG (HIgG) as a model protein. The GNPs/CNTs nanohybrids covered on the glass carbon electrode (GCE) constructed an effective antibody immobilization matrix and made the immobilized biomolecules hold high stability and bioactivity. Enhanced sensitivity was obtained by using bioconjugates featuring HRP labels and secondary antibodies (Ab2) linked to GNPs at high HRP/Ab2 molar ratio. The approach provided a linear response range between 0.125 and 80ng/mL with a detection limit of 40pg/mL. The immunosensor showed good precision, acceptable stability and reproducibility and could be used for the detection of HIgG in real samples, which provided a potential alternative tool for the detection of protein in clinical laboratory. [Copyright &y& Elsevier]

The FKBP (FK506-binding protein) gene family is an important member of the PPlase protease family and plays a vital role during the processes of plant growth and development. However, no studies of the FKBP gene family have been reported in cucumber. In this study, 19 FKBP genes were identified in cucumber, which were located on chromosomes 1, 3, 4, 6, and 7. Phylogenetic analysis divided the cucumber FKBP genes into three subgroups. The FKBP genes in the same subgroup exhibited similar structures and conserved motifs. The cis-acting elements analysis revealed that the promoters of cucumber FKBP genes contained hormone-, stress-, and development-related cis-acting elements. Synteny analysis of the FKBP genes among cucumber, Arabidopsis, and rice showed that 12 kinds of syntenic relationships were detected between cucumber and Arabidopsis FKBP genes, and 3 kinds of syntenic relationships were observed between cucumber and rice FKBP genes. The tissue-specific expression analysis showed that some FKBP genes were expressed in all tissues, while others were only highly expressed in part of the 10 types of tissues. The expression profile analysis of cucumber FKBP genes under 13 types of stresses showed that the CsaV3_1G007080 gene was differentially expressed under abiotic stresses (high temperature, NaCl, silicon, and photoperiod) and biotic stresses (downy mildew, green mottle mosaic virus, Fusarium wilt, phytophthora capsica, angular leaf spot, and root-knot nematode), which indicated that the CsaV3_1G007080 gene plays an important role in the growth and development of cucumber. The interaction protein analysis showed that most of the proteins in the FKBP gene family interacted with each other. The results of this study will lay the foundation for further research on the molecular biological functions of the cucumber FKBP gene family. [ABSTRACT FROM AUTHOR]

Recently, Pt-Y alloy has displayed an excellent electrocatalytic activity for oxygen reduction reaction (ORR), and is regarded as a promising cathode catalyst for fuel cells. However, the bulk production of nanoscaled Pt-Y alloy with outstanding catalytic performance remains a great challenge. Here, we address the challenge through a simple dealloying method to synthesize nanoporous Pt-Y alloy (NP-PtY) with a typical ligament size of ~5 nm. By combining the intrinsic superior electrocatalytic activity of Pt-Y alloy with the special nanoporous structure, the NP-PtY bimetallic catalyst presents higher activity for ORR and ethanol oxidation reaction, and better electrocatalytic stability than the commercial Pt/C catalyst and nanoporous Pt alloy. The as-made NP-PtY holds great application potential as a promising electrocatalyst in proton exchange membrane fuel cells due to the advantages of facile preparation and excellent catalytic performance. [ABSTRACT FROM AUTHOR]

The key step in the fabrication of highly active electrochemical sensors is seeking multifunctional nanocomposites as electrode modified materials. In this study, the gold nanoparticle-decorated helical carbon nanotube nanocomposites (AuNPs-HCNTs) were fabricated for rutin detection because of its superior sensitivity, the chemical stability of AuNPs, and the superior conductivity and unique 3D-helical structure of helical carbon nanotubes. Results showed the prepared nanocomposites exhibited superior electrocatalytic activity towards rutin due to the synergetic effects of AuNPs and HCNTs. Under the optimized conditions, the developed sensor exhibited a linear response range from 0.1 to 31 μmol/L for rutin with a low detectable limit of 81 nmol/L. The proposed method might offer a possibility for electrochemical analysis of rutin in Chinese medical analysis or serum monitoring owing to its low cost, simplicity, high sensitivity, good stability, and few interferences against common coexisting ions in real samples. [ABSTRACT FROM AUTHOR]

Nitrogen-doped carbon nanotubes (N-CNTs)/gold composites were synthesized through a simple self-assembly method. The morphology, composition, and optical properties of the resulted composites were investigated by transmission electron microscopy, scanning electron microscopy, X-ray diffraction, Raman spectra, ultraviolet-visible absorption spectrum, and X-ray photoelectron spectroscopic. This nanocomposite combines the advantages of N-CNTs and gold nanoparticales showing many excellent properties such as good dispersibility in water and satisfactory biocompatibility. Cyclic voltammogram experiment shows that N-CNTs/gold composite has high conductivity. Based on these aspects, N-CNTs/gold-modified electrode was applied to the voltammetric determination of thioridazine hydrochloride (TH) successfully. The linear calibration range for the TH sensor was 12 ~ 850 μM with a detection limit of 1.3 μM at a signal-to-noise ratio of 3, long-term stability, and good reproducibility. [ABSTRACT FROM AUTHOR]

Abstract: A novel quantum dots (QDs) ECL biosensor for the detection of lysozyme was developed. Lysozyme was first incubated with probes immobilized at Au electrode in order to form the aptamer-lysozyme bioaffinity complexes. And the free probes were hybridized with the 5′-biotin modified cDNA oligonucleotides to form double-stranded DNA (ds-DNA) oligonucleotides. Avidin-QDs were bound to these hybridized cDNA through the biotin-avidin-system. The ECL signal of the biosensor was responsive to the amount of QDs bonded to the cDNA oligonucleotides, which was indirectly inverse proportional to the combined target protein. [Copyright &y& Elsevier]

Three-dimensional nanoporous PtSi (NP-PtSi) alloy was prepared by dealloying ternary PtSiAl alloy ribbons. By combining the nanoporous morphology of PtSi and graphene (GR), a new composite material was developed, which was used to modify the surface of a glassy carbon electrode (GCE). The resulting modified electrodes showed an excellent electrocatalytic activity towards the electro oxidation of bisphenol A. Based on differential pulse voltammetry measurements, NP-PtSi/GR/GCE showed linear response over the concentration range 0.30 to 85 μM bisphenol A, while the detection limit was found to be 0.11 μM (S/N = 3). NP-PtSi/GR/GCE showed also satisfactory stability and selectivity over various compounds present in real samples, and they were successfully applied to the determination of bisphenol A in inoculated milk samples. [ABSTRACT FROM AUTHOR]

Abstract Bimetallic nanoporous alloys have attracted considerable attention for electrochemical sensor applications due to their excellent electrocatalytic activity and structural stability. In the present work, nanoporous PtFe (NP-PtFe) alloy was fabricated by chemical dealloying ternary PtFeAl alloy ribbons. The structure and morphology of NP-PtFe alloy was characterized by scanning electronmicroscopy, transmission electron microscopy and X-ray diffraction. A highly sensitive and selective biosensor based on NP-PtFe alloy and graphene was successfully developed for direct detection of bisphenol A. Under optimal conditions, the proposed sensor showed an efficient electrocatalytic activity towards the redox of bisphenol A. Differential pulse voltammetry was applied to the electrochemical determination of bisphenol A with a wide linear concentration range from 0.2 μM to 96 μM and a low limit of detection of 0.17 μM (S/N = 3). This strategy provides a novel and simple approach for sensitive and selective detection of bisphenol A, holding promising applications in the determination of organic pollution in real water samples. [ABSTRACT FROM AUTHOR]

Recently, a new type of exchange bias (EB) after zero-field cooling has attracted considerable interest mainly in bulk magnetic competing systems. Here, we use a detailed magnetotransport investigation to probe the ground state and zero-field cooled EB (ZEB) in Mn 50 Ni 41 Sn 9 ribbon. Both ZEB and field cooled EB were detected in magnetoresistance results consistent with magnetic measurement. A pure spin-glass ground state is proposed based on parabolic shape of low-field magnetoresistance combined with AC magnetization, memory effect. The appearance of ZEB is attributed to the field-induced nucleation and growth of ferromagnetic domains in the spin glass matrix forming unidirectional anisotropy at the interface. [ABSTRACT FROM AUTHOR]

Three-dimensional nanoporous copper (NPC) was fabricated by dealloying ribbons of an Al-Cu alloy. NPC possesses a clean metal surface and high electrical conductivity. Subsequently, a non-enzymatic electrochemical sensor was obtained by modifying a glassy carbon electrode with nanocomposites containing nanoporous copper and carbon black (NPC-CB) in a nafion matrix. The sensor, if operated at a working voltage of 0.6 V (vs. SCE) in 50 mM NaOH solution, has a linear analytical range that extends from 6.0 μM to 3.4 mM of glucose, and a 2.6 μM detection limit (at an S/N ratio of 3). It also shows good selectivity over ascorbic acid, uric acid, dopamine and carbohydrates (fructose, saccharose, and maltose). The sensor also has a rapid amperometric response to hydrogen peroxide which can be quantified with a 1.2 μM detection limit. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

A nanocomposite consisting of helical carbon nanotubes, polyallylamine hydrochloride and CdSe quantum dots was synthesized and used for the electrochemiluminescent determination of dopamine in presence of peroxodisulfate. The nanocomposite was characterized by transmission electron microscopy, UV-absorption and photoluminescence spectroscopy. The electrochemical process was characterized by cyclic voltammetry and electrochemical impedance spectroscopy. Under optimized conditions, the ECL intensity decreases linearly with the concentration of dopamine in the 1.0 × 10 mol · L to 2.0 × 10 mol · L range, with a 0.2 × 10 mol · L detection limit. The method represents a rapid, simple and sensitive protocol for the determination of dopamine. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Theadsorption process of salicylic acid (SA) onto chitosan membraneis monitored in real time by the dielectric relaxation spectroscopy(DRS) method. A unique dielectric relaxation, which is related tothe macroscale concentration polarization layers (CPLs) in the SAsolution caused by the adsorption, is observed. By modeling the measuredsystems composed of the membrane, the CPLs, and the SA solution, thedielectric spectra are analyzed systematically on the basis of theinterfacial polarization theory. The parameters about the constituentphases, i.e., the dielectric constant εmand theconductivity κmof the chitosan membrane, the conductivitydistribution (κ1to κ2), and thethickness dCPLof the CPL, are obtained.The time-dependent εmand κmgiveinsight into the microstate of the chitosan membrane during the adsorption.Furthermore, the time evolution of the conductivity gradient of theCPL, Δκ/dCPL, is combinedto interpret the adsorption mechanism. It is suggested that the noninvasivedielectric monitoring may be applied to many adsorption and releaseprocesses. [ABSTRACT FROM AUTHOR]

Abstract: Series of Dy(Co1− x Mn x )2 alloys (x =0, 0.02, 0.04, 0.06, 0.08, and 0.1) have been prepared by arc-melting method. All samples crystallize in single phase with C15 cubic MgCu2-type structure. The nature of phase transition was determined by the results of Arrott plots and Ac susceptibility, and no first order phase transition was observed for samples with x ⩾0.02. With the increase of Mn content, Curie temperature increases linearly, while the calculated magnetic entropy change shows an obvious decrease with a broader peak, which could be explained by the change of phase transition type. [Copyright &y& Elsevier]

Three-dimensional nanoporous copper (NP-Cu) for the first time has been used as an enhanced material for ultrasensitive detection of carbendazim by electrochemistry method. The NP-Cu was fabricated by dealloying Al Cu alloy ribbons, which was characterized by scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The NP-Cu shows bicontinuous nanoporous structure with ligaments of ~20 nm. Based on the large specific surface area and high electrocatalytic activity, the NP-Cu was used to develop an amperometric sensor for carbendazim detection. Sensing parameters such as accumulation time, suspension volume, pH, scan rate, and concentration of carbendazim were discussed. The sensor can be applied to quantification of carbendazim in the concentration range of 0.5–30 μM (R2 = 0.998), with a detection limit of 0.09 μM (S/N = 3). Moreover, the sensor showed good stability, high selectivity, and satisfactory anti-interference ability. The proposed approach was approvingly applied to electrochemical determination of carbendazim in practical sample. • Electrochemical carbendazim sensor using three-dimensional nanoporous Cu/graphene composite • The sensor exhibits low detection limit, wide linear range, high sensitivity and stability. • The sensor was successfully applied to the analysis of carbendazim in pond water. [ABSTRACT FROM AUTHOR]